Dynamic headlamp aim buy-off window

Abstract

A method for aiming headlamps on a vehicle achieves a reduced variation in beam heights without making any changes to existing test equipment. A cutoff height of a first headlamp is measured. The first headlamp is adjusted until a first measured cutoff height is within a predetermined range centered on a predetermined fixed height. A cutoff height of a second headlamp is measured. The second headlamp is adjusted until a second measured cutoff height is within the predetermined range centered on the first measured cutoff height.

What is claimed is: 
     
       1. A method of aiming headlamps on a vehicle, comprising the steps of:
 measuring a cutoff height of a first headlamp; 
 adjusting the first headlamp until a measured first headlamp cutoff height is within a buy-off range centered on a predetermined fixed height; 
 measuring a cutoff height of a second headlamp; 
 adjusting the second headlamp until a measured second headlamp cutoff height is within a dynamic range centered on the first headlamp adjusted cutoff height. 
 
     
     
       2. The method of  claim 1  wherein the first and second headlamps are each on a respective one of the left and right sides of the vehicle. 
     
     
       3. The method of  claim 1  wherein the adjusting steps are each comprised of a series of incremental adjustments made by a robotic adjuster. 
     
     
       4. The method of  claim 1  wherein an automatic aimer system is configured to 1) perform the measuring and adjusting steps for the first headlamp, 2) store the measured first headlamp cutoff height, 3) move from the first headlamp to the second headlamp on a movable support system, and 4) perform the measuring and adjusting steps for the second headlamp. 
     
     
       5. A headlamp aiming system for aiming first and second headlamps of a vehicle, comprising:
 an aimer for receiving illumination produced by the first and second headlamps to measure first and second headlamp cutoff heights, respectively; 
 a computer for receiving the first and second headlamp cutoff heights from the aimer; and 
 an adjuster for operatively coupling to the vehicle for executing adjustments of the first and second headlamps to incrementally modify the first and second headlamp cutoff heights in response to commands from the computer; 
 wherein the computer is programmed to perform the steps of:
 a) measuring the first headlamp cutoff height; 
 b) comparing the first headlamp cutoff height to a buy-off window, wherein the buy-off window is a predetermined range centered on a predetermined fixed height; 
 c) if the first headlamp cutoff height is outside the buy-off window, then commanding an incremental adjustment of the first headlamp in a direction to move the first headlamp cutoff height toward the buy-off window and then returning to step a; 
 d) if the first headlamp cutoff height is within the buy-off window, then storing the first headlamp cutoff height; 
 e) measuring the second headlamp cutoff height; 
 f) comparing the second headlamp cutoff height to a dynamic window, wherein the dynamic window is centered on the stored first headlamp cutoff height, wherein the size range of the dynamic window is the same size range as the buy-off window, and wherein the height of the dynamic window is non-identical to the buy-off window; 
 g) if the second headlamp cutoff height is outside the dynamic window, then commanding an incremental adjustment of the second headlamp in a direction to move the second headlamp cutoff height toward the dynamic window and then returning to step e; 
 h) if the second headlamp cutoff height is within the dynamic window then ceasing adjustment of the second cutoff height. 
 
 
     
     
       6. The system of  claim 5  wherein the adjuster is a robotic alignment system for automatically executing the adjustments in response to the commands.